Acoustic and NMR investigations of melting and crystallization of indium–gallium alloys in pores of synthetic opal matrices

The paper presents the results of studying the crystallization and melting processes of Ga–In eutectic alloys, which are embedded in opal matrices, using acoustic and NMR methods. The indium concentrations in the alloys were 4, 6, 9, and 15 at %. Measurements were performed upon cooling from room temperature to complete crystallization of the alloys and subsequent heating. It is revealed how the size effects and alloy composition influence the formation of phases with α- and β-Ga structures and on changes in the melting-temperature ranges. A difference was observed between the results obtained using acoustic and NMR methods, which was attributed to different temperature measurement conditions.     

Pretreatment for Simultaneous Production of Total Lipids and Fermentable Sugars from Marine Alga, Chlorella sp.

The goal of this study was to determine the optimal pretreatment process for the extraction of lipids and reducing sugars to facilitate the simultaneous production of biodiesel and bioethanol from the marine microalga Chorella sp. With a single pretreatment process, the optimal ultrasonication pretreatment process was 10 min at 47 KHz, and extraction yields of 6.5 and 7.1 (percentage, w/w) of the lipids and reducing sugars, respectively, were obtained. The optimal microwave pretreatment process was 10 min at 2,450 MHz, and extraction yields of 6.6 and 7.0 (percentage, w/w) of the lipids and reducing sugars, respectively, were obtained. Lastly, the optimal high-pressure homogenization pretreatment process was two cycles at a pressure of 20,000 psi, and extraction yields of 12.5 and 12.8 (percentage, w/w) of the lipids and reducing sugars, respectively, were obtained. However, because the single pretreatment processes did not markedly improve the extraction yields compared to the results of previous studies, a combination of two pretreatment processes was applied. The yields of lipids and reducing sugars from the combined application of the high-pressure homogenization process and the microwave process were 24.4 and 24.9 % (w/w), respectively, which was up to three times greater than the yields obtained using the single pretreatment processes. Furthermore, the oleic acid content, which is a fatty acid suitable for biodiesel production, was 23.39 % of the fatty acids (w/w). The contents of glucose and xylose, which are among the fermentable sugars useful for bioethanol production, were 77.5 and 13.3 % (w/w) of the fermentable sugars, respectively, suggesting the possibility of simultaneously producing biodiesel and bioethanol. Based on the results of this study, the combined application of the high-pressure homogenization and microwave pretreatment processes is the optimal method to increase the extraction yields of lipids and reducing sugars that are essential for the simultaneous production of biodiesel and bioethanol.     

A Molecular Circuit Regenerator to Implement Iterative Strand Displacement Operations

The predictable chemistry of Watson–Crick base-pairing imparts a unique structural programmability to DNA, enabling the facile design of molecular reactions that perform computations. However, many of the current architectures limit devices to a single operational cycle. Herein, we introduce the design of the “regenerator”, a device based on coupled enthalpic and entropic reactions that permits the regeneration of molecular circuit components.     

Multistage homotopy perturbation method for nonlinear reaction networks

In this paper, we present the multistage homotopy perturbation method for finding the solution of the chemical kinetics with nonlinear reactions. We develop a general scheme for finding the analytic solution of chemical reaction networks and apply it to motivating chemical examples such as the enzyme kinetics model and the Brusselator model. We illustrate the numerical result for the models and show the accuracy of the method.     

A Fully Non-Contact Ultrasonic Propagation Imaging System for Closed Surface Crack Evaluation

Cracks are one of the most common types of damage occurring in engineering structures. A reliable nondestructive evaluation technique is essential to detect any possible damage at the initiation phase. Real fatigue closed-surface cracks are difficult to detect through visual inspection. Ultrasound has been widely used, but conventional contact ultrasonic inspection techniques are not suitable for couplant-sensitive structures. In addition, these techniques are generally laborious for large field structures and the inspection speed is relatively slow. We present a novel fully non-contact hybrid ultrasonic propagation imaging (UPI) system that uses laser ultrasonic scanning excitation and piezoelectric air-coupled sensing. Ultrasonic frequency tomography and wavelet-transformed ultrasonic propagation imaging algorithms are used to extract damage features. These features are used to perform a thorough diagnosis of damage. The system enables remote and fully non-contact automatic one-sided inspection for temporal reference-free damage evaluation, and is also applicable to in-field structures. Optimization provides improved performance of air-coupled transducers (ACTs) used as receivers for the hybrid UPI system, as shown by our experimental results. Surface crack evaluation results were analyzed on the basis of ease of damage visualization, accuracy of crack size estimation, and sensitivity. The proposed hybrid UPI system is sensitive enough to detect a real fatigue closed-surface micro-crack with size detection accuracy as high as 96%. We also show that the relation between the scanning interval and crack width affects damage visualization performance, and the accuracy and sensitivity of damage size estimation.     

Characterization of Oil-Wax Gel with Higher Velocity Gradient

The properties of solid surface on oil-wax gel are one of the most important factors which decide the quality of products such as cosmetics. The thixotropic property of solid surface depends on the velocity gradient and it is increased with higher velocity gradient as controlling the morphology on solid surface of oil-wax gel. The morphological change of oil-wax gel in compliance with surface properties of wax matrix can cause different rheological behaviors. Rheological behavior of oil-wax gel regarding the surface transition range in accordance with shear strain was observed to characterize surface properties. In an earlier article, the morphological mechanism of causing surface transition range and the factors of influencing surface transition range were examined by studying the rheological behaviors of a solid-state emulsion. Here, we investigated, in the lattice structure terms, the morphological change of oil-wax gel by measuring surface transition range depending on velocity gradient, which could influence the hardness and sweating phenomenon. We confirmed that the morphological change of oil-wax gel was accompanied by crystal size, crystal conformation, the degree of crystallinity. Surface transition range depending on velocity gradient was shown in large and regular lattice structure of oil-wax gel better than small and irregular one.     

Dispersion Stability of Fluorinated Multi-Walled Carbon Nanotubes in FC-27 Refrigerant

In order to achieve the dispersion stability of multi-walled carbon nanotubes (MWCNT) in a fluorinated refrigerant (FC-72) used in various cooling purposes, fluorinated MWCNT (MWCNT-F) was prepared by a combined process of oxidation and fluorination. As a fluorine source, (tridecafluoro-1,1,2,2-tetrahydrooctyl)trichlorosilane was used to react with hydroxyl groups on MWCNT (MWCNT-OH) generated by chemical oxidation. Pristine MWCNT, MWCNT-OH, and MWCNT-F were dispersed in FC-72 and MWCNT-F was also dispersed in polar and nonpolar solvents. The MWCNT-F has excellent colloidal stability in FC-72 because of the chemical affinity between FC-72 and functional groups (-CF_n) on the side walls of MWCNT. Through surface modifications, we could obtain the enhanced dispersion stability of MWCNT in a refrigerant. This homogenous MWCNT solution in FC-72 may be used to increase the heat transfer in FC-72 based nanofluids.